This is to request funding for a FEI Tecnai G2 F30 High Resolution Transmission Electron Microscope for Structural Biology equipped for tomography and single particle analysis. Tomography provides the highest spatial resolution available for studying cellular organelles in situ or in vitro, while single particle analysis provides the best resolution for studying isolated purified molecules that can not be crystallized. Detailed structural knowledge of organelles and molecules is essential for understanding mechanisms of diseases and developing treatments for them. The microscope would initially support the NIH sponsored research of three well-established investigators at Stanford University School of Medicine: U.J. McMahan, Roger D. Komberg and Stephen J Smith. All are using tomography or single particle analysis in their investigations. With its accompanying equipment, there is no better electron microscope available for the various intended uses of the investigators. These range from determining the structure of molecules at near-atomic resolution (RDK) to characterizing the macromolecular architecture and function of certain organelles crucial for impulse transmission at synapses in the nervous system (UJM) to tracking specific proteins during different stages of synapse formation in order understand their role in that process (SJS). There are currently no other investigators in the broad biomedical research program at Stanford conducting research relying on use of the microscope. However its availability and the usefulness of tomography/single particle analysis would be advertised through a website listing all core facilities and resources at the Medical School and through a lecture/techniques course taught by UJM, RDK, and SJS. Users would be able to schedule time on the microscope via a website as done for other comparable resources at Stanford. The microscope would be generally maintained by a career electron microscope specialist currently in the PI's lab, R.M. Marshall, who has operated microscopes similar to the one proposed. He would also train new users how to operate it, or he would operate it for them. A programmer would be employed part time to maintain and upgrade the software. The maintenance would be financed by an annual operating budget administered through the PT's department by a "service center", as done for other Stanford facilities and resources. The service center would bill users monthly according to their level of usage. This would be the first electron microscope of its type at Stanford.